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I was at an event this evening in a restored ballroom - absolutely beautiful, but parquet flooring, high ceilings, solid walls etc all made for terrible acoustics, and in fact I could hardly make out the voice of the individuals on stage.

I think it is safe to say the venue will not be modifying the hall physically, so are there active solutions or mitigations for this scenario?

(I'm thinking something like noise cancellation, but not sure how that would work)

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Also a good fit for AVP SE. –  American Luke Nov 9 '12 at 0:26

5 Answers 5

up vote 12 down vote accepted

Noise cancellation never works on scales larger than the sound's wavelength, so it's only useful for headphones.

Modifying the hall physically is the only real solution to this problem.

Short of that, the first thing to try is indeed to bring the sound as directly to the audience as possible, by using a suitable PA arrangement. Big, single speakers located "out of sight" are generally worse than multiple speakers close to the audience, either at different levels (delay lines) or as a stack (approximate line array, which partially cancels the sound that goes to the ceiling).

If that's not enough, the only thing you can do is modify the sound signals itself. Obviously, a small acoustic ensemble will have less of a problem with reverb than a large, loud rock band. In particular, uncompressed drum accents cause reverb throughout the frequency spectrum that often overpowers everything else. So you want to make the drums themselves as quiet as possible. The monitor levels should also be kept down, because those signals arrive at the audience only indirectly.
Then, on the PA, you should aim at a strongly frequency-separated mix and rather agressive compression. This way, all instruments should come through reasonably well even when the time-domain is completely smeared out by the reverb.

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I know that sometimes for concerts there will be "shells" around the ensemble, curving down and around the group. This will help reduce any noise escaping backwards. Not knowing the venue, this may not be part of the problem.

It also depends on whether or not the ensemble is acoustic or electric. With electric you could point the speakers in different ways to avoid bouncing the sound off of the walls or what-have-you. If it's acoustic, look into speakers and mics.

You could also pack the hall full of people! Or chairs. Or some other kind of buffer. Were there curtains on the windows? Make sure they're closed. You just want to avoid having "shiny" surfaces and want something your sound can grip onto.

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Pointing the speakers one way or another won't help much. Eventually the sound will hit a wall, or chairs, or the low ceiling, or ceiling beams if you're indoors and start bouncing. You need sound absorption, and that means soft squishy stuff, like people, or rugs, or sound baffles or egg cartons -- something that absorbs it. –  the Tin Man Nov 9 '12 at 5:14
    
Ah, good point. Acoustic bias here. :-P –  user3169 Nov 9 '12 at 5:16
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Sadly even with a full turnout of people in chairs, the majority of the room is still empty. Ceilings are maybe 50-60 feet. No curtains. Floor to ceiling windows and mirrors. Not an ideal environment. –  Dr Mayhem Nov 9 '12 at 8:35
    
Ouch. Good luck! If you find a solution let us know! –  user3169 Nov 10 '12 at 5:31

If you can't treat the room, you can try optimizing using the sound system and the band.

  1. Control sound radiation so it beams as much as possible towards the audience and absorptive surfaces and away from any reflective surfaces.
  2. Monitor wedges are the worst. They beam up and back directly at backwall and ceiling. Wedges have their place on large stages but in smaller venues they are often unnecessary and considerably muddy the sound in the audience.
  3. Easy on the bass. It's very difficult to control directivity at low frequencies and also room reverb energy is the highest in this range. Best shot is to keep it overall on the low side.
  4. Vertical control is particularly important. Small portable line arrays (Bose, Fishman, etc.) are quite good at keeping the sound horizontally confined. Horns-based are very bad at this. If you have a horn on a stick, try tilting it downwards (if this can be done safely).
  5. Keep the volume down. The overall loudness in the room is a function of both the energy you put in and the reverb time of the room. You need to put in less sound energy than usual.
  6. If possible adjust playing style and arrangements. You may be itching to crank out that lick of 32nd notes you have been practicing all year, but in this case a few well placed and well balanced long notes may work better.
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You don't have to modify the room to add physical damping to it. Velvet drapes absorb a lot of sound, even when they don't actually cover any surface, and would be very sympathetic to the decor. A few loose rugs covering unused floor areas, where the audience isn't directly looking at them, would also help a lot. The drapes and rugs could be put in place right before the event and removed at the end: they're just another piece of equipment for the event, like the PA system and the seating.

Aside from this, music in acoustically poor spaces relies a lot on singing/playing technique. Performers have to be warned in advance that the space is "boomy", so they know to play appropriately. Don't forget that a ballroom is purpose-made for a small acoustic instrumental ensemble, and any other kind of performer will have to adapt to sound more like that.

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Another thing you can use is a high quality digital delay for the high frequencies through the stage mains since they travel faster then the bass frequencies. Things will sound less muddled. You can also use a 3rd and 4th speaker in the back of the room with the live mix delayed on the stage mains and the rear or mid-room speakers non-delayed. Van Halen and Pink Floyd have had microphones measuring the volumes of many points in the stadium.

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